To put that in context its market capitalisation before the announcement was just £29.69mln.
It is markedly higher now, with the shares up 42.31% or 5.5p at 18.5p having earlier been as high as 22p.
The Australia-headquartered coal company alleges that the Republic of Poland breached its obligations in blocking the development of its Jan Karski and Debiensko mines, thus depriving it of the entire value of its investments in Poland.
The £806mln includes an assessment of the value of lost profits as well as damages and accrued interest.
The company has a US$12.3mln litigation funding agreement in place which is currently being drawn down to cover legal, tribunal and external expert costs and operating expenses associated with the claim.
Chief executive Ben Stoikovich said: "The claim is proceeding at pace, with the company now having submitted its statement of claim in the Bilateral Investment Treaty arbitration, which included a valuation of damages prepared by external quantum experts."